Research Of Performance Of UHPC Incorporating HCSA Expansion Agent

Ultra High Performance Concrete (Ultra-High Performance Concrete，UHPC) is acement-based material with high strength, high toughness, low porosity. As a newcomposite material with excellent performance, it will be widely used in the future.Shrinkage of concrete is the volume decrease caused by water changes, chemicalreactions and temperature changes in the concrete. Shrinkage is mainly divided intofive categories, namely, plastic shrinkage, autogenous shrinkage, drying shrinkage,temperature shrinkage caused by temperature drop and carbonation shrinkage. Thetensile stress of concrete occurs when the shrinkage happens, When the ultimatetensile stress exceeds the tensile strength of concrete will cause the concrete to crack,thereby affecting its performance and durability.Shrinkage stress of ordinary concrete mainly refers to the shrinkage caused bydrying shrinkage stress. But UHPC, due to its low water-cement ratio and largeamount of reactive powder incorporated, the autogenous shrinkage of UHPC plays aleading role in total shrinkage. Therefore, it is very important to find ways to controlshrinkage cracks in the application of UHPC.Due to huge demand, Shrinkage-compensating concrete incorporated expansiveshrinkage are widely used in engineering, research of new expansive and actionprincipl of shrinkage-compensating concrete are particularly important.In order to reduce shrinkage，reduce cracking and improve the performance ofUHPC, high performance expansive HCSA(High Performance Calcium SulphoAluminate, HCSA) was selected as ultra-high performance concrete admixtures byusing of shrinkage-compensating principle.In order to gain better understand of the impact of HCSA expansive to ultra highperformance concrete, paper studies the following:(1) By measuring the fluidity and setting time of UHPC in different expansionagent types, different water-cement ratio and different dosage of expansive, theinfluence of HCSA on work performance of UHPC is founded.(2) Measured the volume change in different expansion agent types, differentwater-cement ratio and different dosage of expansive of UHPC by bellow test, theinfluence of HCSA on autogenous shrinkage of ultra-high performance concrete isresearched. (3) Measured the volume change of UHPC by Tester of Concrete ShrinkageStrain, the influence of HCSA with and without steel fibers on dry shrinkage ofultra-high performance concrete are investaged.(4) By measuring the flexural strength and compressive strength in differentcontent, different water-cement ratio and different curing age of UHPC, the influenceof HCSA on mechanical properties of UHPC is founded. And through SEM and DSC,the effect of HCSA on the mechanical properties of UHPC is analyzed, from themicro-structural prospect of view. Finally, by measuring the compressive strength ofUHPC with steel fiber, the influence of HCSA on UHPC with steel fiber is investaged.